1. Field of the Invention
The present invention relates generally to a transport mechanism, and more particularly to a circulating latch transport mechanism which permits motion in two dimensions on a planar array of parallel ceiling beams while maintaining firm mechanical attachment to the beam structure.
2. Discussion of Prior Art
Currently there are a variety of materials handling systems which are flexible in the sense that a variety of paths and destinations for the cargo may be selected, and a variety of cargos may be transported. For example, forklift trucks can carry a variety of palletized cargo and can transport this cargo anywhere ina warehouse or manufacturing complex. By contrast, conveyor belt systems are usually much more specialized and inflexible.
Some examples of prior art mobile handling systems are shown in the following references.
HENDRICKS, U.S. Pat. No. 3,398,806, discloses a self-propelled construction-type mobile platform which carries objects over corrugated or ribbed supporting surfaces.
SHIO, U.S. Pat. No. 3,960,229, discloses a motordriven vehicle which may be used on flat or inclined surfaces. The vehicle is provided with electromagnetic pads or shoes on continuous tractor belts. As the shoes pass along the bottom of the tractor belts, an electromagnetic force can be generated to prevent the vehicle from falling from an inclined surface. The surface must be magnetizable and is preferably made of steel. A typical use for such a vehicle would be transportation on a ship's hull.
STEEDMAN, U.S. Pat. No. 1,053,545, discloses a crane which is positioned below a bridge and supported by parallel I-beams such that the lower flanges of the I-beams serve as tracks for the wheels of the crane.
Most flexible materials handling systems can be classified as floor-based systems or ceiling-based systems. For example, forklift trucks are flor-based, while overhead cranes may be thought of as ceiling-based. In general, floor-based systems are simpler to operate and more economical, but require a great deal of floor space. Typical floor-based systems also include carts, dollies, towline systems and mobile pallet systems. In the case of mobile pallet systems, the cargo is mounted ona skid or pallet which rests on wheels or a pneumatic cushion. The pallet may be self-propelled or pulled by a tow-cable system. Self-propelled pallets may be computer controlled and may be adapted to follow guide wires embedded in the floor.
The most common overhead or ceiling-based system is the standard overhead crane. Overhead cranes are a preferred method for handling materials since they do not use floor space which can then be allocated for other purposes. However, no current overhead materials handling systems have the flexibility of the motorized pallet systems or of forklift trucks, and most are not easily adaptable to computer control. In addition, it is often the case that more than one overhead crane is operated in the same crane bay in order to speed materials handling. A problem often results when cranes sharing the same bay get in the way of each other. This is known as interference between cranes. In some industries this problem is serious enough to require computer simulations in order to minimize the impact on production.